Durham University

About: Durham University is a education organization based out in Durham, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 39385 authors who have published 82311 publications receiving 3110994 citations. The organization is also known as: University of Durham & Gallery of Durham University.

Stable clustering, the halo model and non-linear cosmological power spectra

Abstract: We present the results of a large library of cosmological N-body simulations, using power-law initial spectra.

A framework linking intangible resources and capabilities to sustainable competitive advantage

Abstract: This article is concerned with the role of intangible resources in business strategy. In particular it is concerned with identifying the intangible sources of sustainable competitive advantage. Sustainable competitive advantage results from the possession of relevant capability differentials. Regulatory and positional capabilities are concerned with intangible assets; functional and cultural capabilities are concerned with competencies. A framework linking intangible resources to capabilities has been devised and is used as the basis of a new technique for identifying the relative contribution which the different intangible resources make to competitive advantage. The results of the use of this technique in six case studies are reported.

Predictors of hospital mortality in the global registry of acute coronary events.

Abstract: Background Management of acute coronary syndromes (ACS) should be guided by an estimate of patient risk. Objective To develop a simple model to assess the risk for in-hospital mortality for the entire spectrum of ACS treated in general clinical practice. Methods A multivariable logistic regression model was developed using 11 389 patients (including 509 in-hospital deaths) with ACS with and without ST-segment elevation enrolled in the Global Registry of Acute Coronary Events (GRACE) from April 1, 1999, through March 31, 2001. Validation data sets included a subsequent cohort of 3972 patients enrolled in GRACE and 12 142 in the Global Use of Strategies to Open Occluded Coronary Arteries IIb (GUSTO-IIb) trial. Results The following 8 independent risk factors accounted for 89.9% of the prognostic information: age (odds ratio [OR], 1.7 per 10 years), Killip class (OR, 2.0 per class), systolic blood pressure (OR, 1.4 per 20-mm Hg decrease), ST-segment deviation (OR, 2.4), cardiac arrest during presentation (OR, 4.3), serum creatinine level (OR, 1.2 per 1-mg/dL [88.4-µmol/L] increase), positive initial cardiac enzyme findings (OR, 1.6), and heart rate (OR, 1.3 per 30-beat/min increase). The discrimination ability of the simplified model was excellent with c statistics of 0.83 in the derived database, 0.84 in the confirmation GRACE data set, and 0.79 in the GUSTO-IIb database. Conclusions Across the entire spectrum of ACS and in general clinical practice, this model provides excellent ability to assess the risk for death and can be used as a simple nomogram to estimate risk in individual patients.

A covariant holographic entanglement entropy proposal

Abstract: With an aim towards understanding the time-dependence of entanglement entropy in generic quantum field theories, we propose a covariant generalization of the holographic entanglement entropy proposal of hep-th/0603001. Apart from providing several examples of possible covariant generalizations, we study a particular construction based on light-sheets, motivated in similar spirit to the covariant entropy bound underlying the holographic principle. In particular, we argue that the entanglement entropy associated with a specified region on the boundary in the context of the AdS/CFT correspondence is given by the area of a co-dimension two bulk surface with vanishing expansions of null geodesics. We demonstrate our construction with several examples to illustrate its reduction to the holographic entanglement entropy proposal in static spacetimes. We further show how this proposal may be used to understand the time evolution of entanglement entropy in a time varying QFT state dual to a collapsing black hole background. Finally, we use our proposal to argue that the Euclidean wormhole geometries with multiple boundaries should be regarded as states in a non-interacting but entangled set of QFTs, one associated to each boundary.

Spectra of some self-exciting and mutually exciting point processes

Abstract: SUMMARY In recent years methods of data analysis for point processes have received some attention, for example, by Cox & Lewis (1966) and Lewis (1964). In particular Bartlett (1963a,b) has introduced methods of analysis based on the point spectrum. Theoretical models are relatively sparse. In this paper the theoretical properties of a class of processes with particular reference to the point spectrum or corresponding covariance density functions are discussed. A particular result is a self-exciting process with the same second-order properties as a certain doubly stochastic process. These are not distinguishable by methods of data analysis based on these properties.